This invention relates to power transmissions and more particularly to power transmissions having multiple countershafts.
Power transmissions with multiple countershafts generally have a housing assembly formed with at least two members that are aligned by dowel pins. These members generally include a casing and an end cover or bell housing. The bell housing generally encloses a torque converter or friction clutch. The countershafts are supported in the casing at one end and in the end cover at the other end. The input shaft is generally supported in the end cover and the output shaft is supported in the casing.
The alignment and parallelism of the shafts is determined by the doweling between the casing and cover and the bearing bores in each of the casing and end cover. The machining of the required dowel and bearing bores is subject to manufacturing tolerances which must be held within close limits for quiet, efficient and durable operation of the transmission. As is well known, close tolerance machining adds to the overall cost of the product.
In the prior art multiple countershaft transmissions, each countershaft in the transmission has a different or distinct configuration. The bearing mounting surfaces and the gear mounting surfaces are machined to specific tolerances and dimensions for each bearing and gear. Lube passages are unique from one countershaft to another. These and other differences require that manufacturing and inventory capabilities must be available for each individual shaft configuration. The number of repair and replacement parts proliferates with each shaft configuration. The end result is an increase in cost for the transmission.